Surface Edit > Orientation > Unify Surface Orientation

Forces sets of adjacent surfaces to have consistent orientations (all facing the same way).

Modifies a collection of patches so that sets of adjacent surfaces face in the same direction (either outward or inward). This helps to ensure that lighting is correct in renderings, and is also useful when modeling, and offsetting surfaces.

This tool modifies the orientation of surfaces based on topology. It is useful to fix surface orientation on smaller parts (for example, a door handle) where it might be difficult to move the camera around in order to see all the surfaces at the same time.

Construction history is preserved during this operation.